using namespace std;
#include<stdio.h>


FILE *fin=fopen("fractii.in","r"),
     *fout=fopen("fractii.out","w");
     

int p[1000220];
long long sol[1000220];
int n;

long long rez;

  void generate()
   {
       unsigned int i,j,k;
       p[1]=0;
       p[2]=0;
       for (i=2; i<=n/2+1; i++)
        {
         k=i*i;
         while (k<=n)
         {
          p[k]=1;
          k+=i;
         }
        }      
   }

 
 void solve()
  {
   unsigned int i,j,k;
   for (i=1; i<=n; i++)
     sol[i]=i;
   for (i=2; i<=n/2; i++)
    if (p[i]==0)
     {
      sol[i]=sol[i]*(i-1)/i;
      k=i+i;
      while (k<=n)
       {
	    sol[k]=sol[k]*(i-1)/i;
	    k+=i;
       }
     }
   for (i=n/2+1; i<=n; i++)
    if (p[i]==0) sol[i]=sol[i]*(i-1)/i;
   rez=0;
 //   fprintf(fout,"%d\n",sol[i]);
  }                     
      

int main()
{
    int i;
    fscanf(fin,"%d",&n);
    generate();
    solve();
    for (i=1; i<=n; i++) rez+=sol[i]; rez=2*rez-1;
    fprintf(fout,"%lld\n",rez);
fclose(fin);
fclose(fout);
return 0;
}